| Cadmium (Cd), existed widely in the nature, was ranked the top one in five of the heavy metal pollutants (Cd,Hg,As,Cr and Pb) as well as in12of the global significant dangerous chemicals which proposed by United Nations Environment Programme. At present, the Cd-contaminated arable land reached20,000,000hm2, which was one fifth of the total arable land worldwide. The increasing content of Cd in soil clearly threatened crop production and food safety. Pepper (Capsicum annum L.) is one of the favorite vegetables and flavorings for people. At the same time, Cd has the tendency of accumulating in pepper, which in turn affectes the taste and quality of pepper and harms human health. The excess amount of Cd in pepper restricts the production and exportation of pollution-free pepper. To investigate the differences of different varieties of pepper in Cd tolerance and accumulation could provide references for the layout planning of Cd-contaminated land in agricultural production. Several methods including engineering, phytoremediation and agronomic regulation method could be used to amend Cd-contaminated soil. In addition, agronomic regulation methods-leaf control technology had the advantages of protecting soil structure and soil microbiological environment. It did not cause any secondary pollution and it was easy to operate on a large scale, for which is had attracted the attention of many researchers.So far, few reports and researches were concerning the selection and mechanisms of cadmium-resistant pepper, even fewer were the influence of Si, P, Zn spraying on Cd assimilation and accumulation for various pepper spices. The author made a comparison of different Cd concentration on pepper seedlings growth, chlorophyll content, antioxidant enzyme activity, plant Cd content of8varieties of pepper. The differences in characteristics of Cd accumulation and related biological properties of these samples were researched and the mechanisms of Si, P, Zn leaf spaying on the Cd assimilation and accumulation were discussed. The results were beneficial for selecting pepper varieties with high-resistance and low-acumulation ability towards Cd and the prevention and control of vegetable Cd pollution. The main conclusions were as follows.1. The growth of peppers was inhabited by Cd (≥20mg·kg-1), with the increasing concentration of Cd in the hydroponics experiment,the plant height,root length,total dry weigh,dry weight of roots, stems and leaves all trended to sustaining decline in8pepper varieties,the plant height,root length and total dry weight of PE39and PE4species were better than other ones,but both were greatly affected by Cd, on the contrary,Cd was the least important factor in both of PE5and PE37species. Cadmium pollution contributed to lower total chlorophyll contents in the leaves of pepper,with the increase of Cd concentration,the total chlorophyll content of pepper decreased significantly,which of PE39declined sharpest among them.lt showed that its structure of chlorophyll were the worst affected.with the increase of Cd concentration.Activities of peroxidase (POD).catalase(CAT) and superoxide dismutase(SOD) showed a tendency to increase with the increase of Cd concentration in the8kinds of Pepper Seedlings.The cadmium content of8Pepper species were in order of roots>stew>leaf and the cadmium accumulation in the root of pepper seedlings was largest,second in stew and minimum in leaf.The accumulation capabilities of cadmium in PE39and PE4species were highest,however,the ones in PE37and PE5species are lower in8pepper species.2. There was different influence of organo and inorgano silicon (2.5mmol·L-1) by method of leaf surface spraying in2varieties of peppers with the pot esperiment,when exposed to Cd(10m g·kg-1).The dry weights of the fruit in the variety of’Shinongchaotianjiao’ increased by28.1%and14.4%compared to the control in.the presence of organo and inorgano silicon,when exposed to Cd,meanwhile,the effects organo silicon produced was better than inorgano silicon in the Shinongchaotianjiao’s body.While the presence of organo and inorgano silicon led to decreased by32.3%and55.1%in dry weights of fruits,compared to the control in the variety of ’Yanjiao425’and the effects inorgano silicon produced was better than organo silicon.Activities of catalase (CAT) and peroxidase (POD) were increased by silicon and were in order of ’organo silicon’>’inorgano silicon’.The fruit cadmium chemical forms in2varieties of peppers were in order of FNaCl>FHAc>FE>Fr>FHCl>FW. The total extractable Cd in fruit of’Shinongchaotianjiao’ obviously decreased by Si compared to the control, while the total extractable Cd in fruit of ’Yanjiao425’ increased. The fruit Cd accumulations of peppers were in order of stew>roots or leaf>fruit.The fruit Cd accumulations in2varieties of peppers obviously decreased by19.1%and23.3%,13.4%and26.1%in the presence of organo and inorgano silicon, when exposed to Cd.The cadmium accumulations in peppers fruit were in order of ’yanjiao425’>’shinongchaotian-jiao’3. Dry weight of total plant and fruit of’Shinongchaotianjiao’increased by P(0.3%and 0.5%) which acted as a stimulus to its growth,while that of ’Yanjiao425’was inhibited by P acted as a inhibitor of its growth with the pot esperiment,when exposed to Cd(10mg-kg-1).Activities of catalase (CAT) were increased at first,and then reduced in the presence of P;Activities of peroxidase (POD) and superoxide dismutase (SOD) of Shinongchaotianjiao’increased with increasing levels of P,however,activities of peroxidase (POD) and superoxide dismutase (SOD) of Yanjiao425’ decreased with increasing levels of P.Chemical forms of Cd in fruit of peppers were in order of FNaCl>FHAc> FE>Fr>FHCl>FW.The total extractable Cd in fruit of ’Yanjiao425’ obviously decreased in the presence of P compared to the control,while the total extractable Cd in fruit of Shinongchaotianjiao’ increased.Cadmium accumulations of peppers were in order of root>stew>leaf>fruit.Cadmium accumulations in fruit and plant of ’Yanjiao425’were decreased by47.7%,58.5%and5.5%,13.1%in the presence of0.3%and0.5%P when exposed to Cd,and Cadmium accumulations in fruit of ’Shinongchaotianjiao’ were decreased by23.6%in the presence of0.5%P compared to the control.4. The biomass of pepper were increased by Zn (≤400μmol·L-1), while inhibited by high Zn (600μmol·L-1) with the pot experiment, when exposed to Cd (20mg·kg-1). Activities of peroxidase (POD), catalase (CAT) and superoxide dismutase (SOD) in the leaves of pepper were reduced by Zn (≤400μmol·L-1).However,activities of peroxidase (POD), catalase (CAT) and superoxide dismutas e(SOD) were increased by high Zn (600μmol·L-1).The main chemical forms of Cd in fruit of pepper were in order of NaCl-extractable Cd>acetic acid-extractable Cd>ethanol-extractable Cd and water-extracta ble Cd.The total extractable Cd,water-extracta ble Cd and ethanol-extractable Cd in fruit were obviously reduced in the presence of Zn compared to the control.Cadmium concentrations in stem,fruit and root of peppers were decreased by2.7%-5.4%,7.5%-28.1%and7.6%-21.8%in the presence of Zn compared to the control when exposed to Cd. |
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